CHROMOSOMECHROMOSOMES AND CELL S AND CELL

REPRODUCTIOREPRODUCTIONN

Section I ChromosomesSection I ChromosomesFormation of New Cells by Formation of New Cells by

Cell DivisionCell Division

.

•New cells are formed when old cells divide.

• 1. Cell division is the same as cell

reproduction.• 2. The type of cell division

differs depending on the organism.

Prokaryotic cellsProkaryotic cells, like, like BacteriaBacteria reproduce byreproduce by

binary binary fissionfission..

•Binary fission: Binary fission: asexual/ a asexual/ a single parent passes exact single parent passes exact copies of its DNA to its copies of its DNA to its offspringoffspring

•11stst stage: stage: DNA is copiedDNA is copied •2nd stage:2nd stage: Cell divides Cell divides

Eukaryotic cells reproduce byEukaryotic cells reproduce by another type of cell division-another type of cell division-

MITOSISMITOSIS

• 1st stage1st stage: : DNA is copiedDNA is copied• chromatidschromatids: : 2 exact copies of DNA 2 exact copies of DNA

that make up a chromosomethat make up a chromosome•centromere: centromere: point of attachment point of attachment of 2 chromatidsof 2 chromatids

• 2nd Stage2nd Stage: : DNA and protein coil into DNA and protein coil into chromosomes chromosomes

• Draw and Label a chromosomeDraw and Label a chromosome::

• The chromatids The chromatids separateseparate during cell division and are during cell division and are each placed into a new cell. each placed into a new cell. This ensures that each cell has This ensures that each cell has the the same genetic informationsame genetic information as the original cell.as the original cell.

• When a cell divides:When a cell divides: the DNA is the DNA is copied 1copied 1stst and then distributed. and then distributed. Each cell ends up with a Each cell ends up with a complete set of the DNA.complete set of the DNA.

Gamete cells- which are Gamete cells- which are spermsperm and and egg egg are created are created

through another type of cell through another type of cell division-division-MEIOSISMEIOSIS

Egg cell surrounded byEgg cell surrounded by

sperm cells.sperm cells.

II. Chromosome Number II. Chromosome Number and Structureand Structure

•Humans have Humans have 4646 chromosomes chromosomes ((23 Pairs23 Pairs) in somatic cells.) in somatic cells.

•Somatic cellsSomatic cells: All body cells : All body cells (except sex cells)(except sex cells)

•GametesGametes: sex cells (sperm and : sex cells (sperm and eggs)eggs)

•Chromosomes differ in Chromosomes differ in size, size, shapeshape and set of and set of genesgenes..

Sets of ChromosomesSets of Chromosomes

•Homologous chromosomes Homologous chromosomes are those that are are those that are paired paired together and are similar in together and are similar in size, shape size, shape andand genetic genetic content.content.

•46 chromosomes = 46 chromosomes = 22 sets sets of of 2323

Diploid- cell contains 2 sets of chromosomes

Haploid- cell contains 1 set of chromosomes

The fusion of 2 haploid cells forms a diploid zygote.

Zygote-fertilized egg cell

B. Sex ChromosomesB. Sex Chromosomes•Out of 23 pairs of Out of 23 pairs of

chromosomes- 22 pairs are chromosomes- 22 pairs are autosomesautosomes; 1 pair are sex ; 1 pair are sex chromosomes.chromosomes.

•Sex chromosomes are the Sex chromosomes are the XX and and YY..

•Male SpermMale Sperm determines the determines the sex of a child.sex of a child.

•XX = FemaleXX = Female XY = XY = MaleMale

C. Change in Chromosome C. Change in Chromosome NumberNumber• There are 1000’s of There are 1000’s of genesgenes on each of on each of

our our chromosomeschromosomes..• The presence of all 46 chromosomes is The presence of all 46 chromosomes is

essential for essential for normal developmentnormal development and and function.function.

• Trisomy- having an Trisomy- having an extra copyextra copy of a of a chromosomechromosome

• Example: Trisomy 21- Example: Trisomy 21- Down’s SyndromeDown’s Syndrome• Cause of Trisomy is Cause of Trisomy is NONDISJUNCTIONNONDISJUNCTION..• This is when the chromosomes don’t This is when the chromosomes don’t

separate separate and one gamete ends up with 2 and one gamete ends up with 2 chromosomes.chromosomes.

Mikey has Down’s Syndrome.Mikey has Down’s Syndrome.He has an extra chromosome. Instead He has an extra chromosome. Instead of having a pair of # 21 chromosomes, of having a pair of # 21 chromosomes,

he as 3 copies of it.he as 3 copies of it.

Karyotype: Karyotype: Normal vs Down’s Normal vs Down’s

SyndromeSyndrome

D. Change in D. Change in Chromosome Structure-Chromosome Structure-

MUTATIONSMUTATIONS •Types of MutationsTypes of Mutations::

1. 1. DeletionDeletion- - piece of chromosome piece of chromosome breaks offbreaks off

2. 2. DuplicationDuplication- - extra chromosome extra chromosome fragment attaches; 2 copies of certain fragment attaches; 2 copies of certain genesgenes

3. 3. Inversion-Inversion- chromosome attaches in chromosome attaches in reverse orderreverse order

4. 4. TranslocationTranslocation – – chromosome piece chromosome piece attaches to a nonhomologous attaches to a nonhomologous chromosomechromosome

See p 124 Draw these See p 124 Draw these Chromosomal MutationsChromosomal Mutations

Section II- The Cell CycleSection II- The Cell CycleA. Cell cycle-Cellular growth A. Cell cycle-Cellular growth

and divisionand division•90%90% of the time is spent inof the time is spent in

Interphase. (preparation to Interphase. (preparation to divide)divide)

•The cell will enter the last 2 The cell will enter the last 2 phases of the cell cycle only if phases of the cell cycle only if it is about toit is about to divide. divide.

5 Phases of the Cell Cycle5 Phases of the Cell CycleThe 1The 1stst 3 stages are part of 3 stages are part of

Interphase.Interphase.• 1. 11. 1stst Growth (G1)- Growth (G1)-Grows rapidly Grows rapidly (nerve cells stay in this stage)(nerve cells stay in this stage)

• 2. Synthesis- 2. Synthesis- DNA is copied; each DNA is copied; each chromosome is copiedchromosome is copied

• 3. 23. 2ndnd Growth (G2)- Growth (G2)- Growth; prep Growth; prep for division; microtubules are for division; microtubules are assembledassembled

• 4. 4. Mitosis- Mitosis- nucleus divides into 2 nucleus divides into 2 nuclei (2 cells) that are identicalnuclei (2 cells) that are identical

• 5. Cytokinesis- 5. Cytokinesis- cytoplasm dividescytoplasm divides

•MitosisMitosis and and cytokinesiscytokinesis produce new cells that produce new cells that are are identicalidentical to the to the original cells and allow original cells and allow organisms to organisms to growgrow, , replace damaged replace damaged tissuetissue, and in some , and in some organisms, organisms, reproducereproduce..

B. How do cells “know” when B. How do cells “know” when to divide? to divide? “Red light- Green “Red light- Green

light”light”

• The cell cycle in eukaryotes is controlled The cell cycle in eukaryotes is controlled by many by many proteins. proteins.

• 1.Cell growth check point(G1): 1.Cell growth check point(G1): makes decision whether cell will makes decision whether cell will dividedivide

•2. DNA synthesis checkpoint2. DNA synthesis checkpoint

(G2): (G2): protein triggers mitosis and protein triggers mitosis and cell begins many processes needed to cell begins many processes needed to proceed into mitosisproceed into mitosis

• 3. Mitosis checkpoint: 3. Mitosis checkpoint: triggers the triggers the exit from mitosis; It signals the exit from mitosis; It signals the beginning of G1.beginning of G1.

• Uncontrolled growth of cellsUncontrolled growth of cells• It is essentially a It is essentially a disorderdisorder of cell of cell

division. division. • Cancer cells do not respond normally to Cancer cells do not respond normally to

the body’s the body’s control mechanismscontrol mechanisms• Some Mutations cause cancer by Some Mutations cause cancer by over-over-

producing growth-promoting molecules, producing growth-promoting molecules, thus speeding up the cell cycle or by thus speeding up the cell cycle or by inactivating the control proteins that inactivating the control proteins that normally act to slow or stop the cell normally act to slow or stop the cell cycle.cycle.

CANCERCANCER--

Section III Mitosis and Section III Mitosis and CytokinesisCytokinesis

•4 stages of Mitosis: 4 stages of Mitosis: 1. Prophase1. Prophase

2.Metaphase2.Metaphase

3. Anaphase3. Anaphase

4. Telophase4. Telophase

ProphaseProphase::•Chromosomes become Chromosomes become visiblevisible, ,

the nuclear envelope dissolves the nuclear envelope dissolves and the and the spindlespindle forms. forms.

•What makes up the spindles? What makes up the spindles? It It is made up of centrioles & is made up of centrioles & individual microtubule fibers; individual microtubule fibers; they are involved in moving the they are involved in moving the chromosomes.chromosomes.

MetaphaseMetaphase• Chromosomes line up in the Chromosomes line up in the

MiddleMiddle (middle phase) (middle phase)

AnaphaseAnaphase• Centromeres Centromeres dividedivide, chromatids , chromatids

move toward move toward oppositeopposite poles. poles.

TelophaseTelophase• Nuclear envelopeNuclear envelope reforms at each reforms at each

pole, chromosomes pole, chromosomes uncoiluncoil , spindle , spindle dividesdivides..

• Mitosis is Mitosis is completecomplete and and cytokinesiscytokinesis begins.begins.

CytokinesisCytokinesis

• Cytoplasm Cytoplasm divides in divides in halfhalf, and , and the membrane the membrane growsgrows to enclose to enclose each cell, each cell, 22 separate cells are separate cells are formed.formed.

A Difference in Plant A Difference in Plant CellsCells

•A cell plate forms across A cell plate forms across the middle of the plant the middle of the plant cell. A new cell wall forms cell. A new cell wall forms on both sides of the cell on both sides of the cell plate. plate.

Put the following in the Put the following in the correct ordercorrect order

• Put the following pictures in the correct Put the following pictures in the correct order as they occur during mitosis:order as they occur during mitosis:

•Answer: c,b,d,aAnswer: c,b,d,a